/* ----------------------------------------------------------------------
* Copyright (C) 2010-2014 ARM Limited. All rights reserved.
*
* $Date:        19. March 2015
* $Revision: 	V.1.4.5
*
* Project: 	    CMSIS DSP Library
* Title:		arm_correlate_opt_q7.c
*
* Description:	Correlation of Q7 sequences.
*
* Target Processor: Cortex-M4/Cortex-M3
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*   - Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*   - Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in
*     the documentation and/or other materials provided with the
*     distribution.
*   - Neither the name of ARM LIMITED nor the names of its contributors
*     may be used to endorse or promote products derived from this
*     software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
* FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
* COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
* BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* -------------------------------------------------------------------- */

#include "arm_math.h"

/**
 * @ingroup groupFilters
 */

/**
 * @addtogroup Corr
 * @{
 */

/**
 * @brief Correlation of Q7 sequences.
 * @param[in] *pSrcA points to the first input sequence.
 * @param[in] srcALen length of the first input sequence.
 * @param[in] *pSrcB points to the second input sequence.
 * @param[in] srcBLen length of the second input sequence.
 * @param[out] *pDst points to the location where the output result is written.  Length 2 * max(srcALen, srcBLen) - 1.
 * @param[in]  *pScratch1 points to scratch buffer(of type q15_t) of size max(srcALen, srcBLen) + 2*min(srcALen, srcBLen) - 2.
 * @param[in]  *pScratch2 points to scratch buffer (of type q15_t) of size min(srcALen, srcBLen).
 * @return none.
 *
 *
 * \par Restrictions
 *  If the silicon does not support unaligned memory access enable the macro UNALIGNED_SUPPORT_DISABLE
 *	In this case input, output, scratch1 and scratch2 buffers should be aligned by 32-bit
 *
 * @details
 * <b>Scaling and Overflow Behavior:</b>
 *
 * \par
 * The function is implemented using a 32-bit internal accumulator.
 * Both the inputs are represented in 1.7 format and multiplications yield a 2.14 result.
 * The 2.14 intermediate results are accumulated in a 32-bit accumulator in 18.14 format.
 * This approach provides 17 guard bits and there is no risk of overflow as long as <code>max(srcALen, srcBLen)<131072</code>.
 * The 18.14 result is then truncated to 18.7 format by discarding the low 7 bits and saturated to 1.7 format.
 *
 *
 */



void arm_correlate_opt_q7(
    q7_t *pSrcA,
    uint32_t srcALen,
    q7_t *pSrcB,
    uint32_t srcBLen,
    q7_t *pDst,
    q15_t *pScratch1,
    q15_t *pScratch2)
{
    q7_t *pOut = pDst;                             /* output pointer                */
    q15_t *pScr1 = pScratch1;                      /* Temporary pointer for scratch */
    q15_t *pScr2 = pScratch2;                      /* Temporary pointer for scratch */
    q7_t *pIn1;                                    /* inputA pointer                */
    q7_t *pIn2;                                    /* inputB pointer                */
    q15_t *py;                                     /* Intermediate inputB pointer   */
    q31_t acc0, acc1, acc2, acc3;                  /* Accumulators                  */
    uint32_t j, k = 0u, blkCnt;                    /* loop counter                  */
    int32_t inc = 1;                               /* output pointer increment          */
    uint32_t outBlockSize;                         /* loop counter                  */
    q15_t x4;                                      /* Temporary input variable      */
    uint32_t tapCnt;                               /* loop counter                  */
    q31_t x1, x2, x3, y1;                          /* Temporary input variables     */

    /* The algorithm implementation is based on the lengths of the inputs. */
    /* srcB is always made to slide across srcA. */
    /* So srcBLen is always considered as shorter or equal to srcALen */
    /* But CORR(x, y) is reverse of CORR(y, x) */
    /* So, when srcBLen > srcALen, output pointer is made to point to the end of the output buffer */
    /* and the destination pointer modifier, inc is set to -1 */
    /* If srcALen > srcBLen, zero pad has to be done to srcB to make the two inputs of same length */
    /* But to improve the performance,
     * we include zeroes in the output instead of zero padding either of the the inputs*/
    /* If srcALen > srcBLen,
     * (srcALen - srcBLen) zeroes has to included in the starting of the output buffer */
    /* If srcALen < srcBLen,
     * (srcALen - srcBLen) zeroes has to included in the ending of the output buffer */
    if(srcALen >= srcBLen)
    {
        /* Initialization of inputA pointer */
        pIn1 = (pSrcA);

        /* Initialization of inputB pointer */
        pIn2 = (pSrcB);

        /* Number of output samples is calculated */
        outBlockSize = (2u * srcALen) - 1u;

        /* When srcALen > srcBLen, zero padding is done to srcB
         * to make their lengths equal.
         * Instead, (outBlockSize - (srcALen + srcBLen - 1))
         * number of output samples are made zero */
        j = outBlockSize - (srcALen + (srcBLen - 1u));

        /* Updating the pointer position to non zero value */
        pOut += j;

    }
    else
    {
        /* Initialization of inputA pointer */
        pIn1 = (pSrcB);

        /* Initialization of inputB pointer */
        pIn2 = (pSrcA);

        /* srcBLen is always considered as shorter or equal to srcALen */
        j = srcBLen;
        srcBLen = srcALen;
        srcALen = j;

        /* CORR(x, y) = Reverse order(CORR(y, x)) */
        /* Hence set the destination pointer to point to the last output sample */
        pOut = pDst + ((srcALen + srcBLen) - 2u);

        /* Destination address modifier is set to -1 */
        inc = -1;

    }


    /* Copy (srcBLen) samples in scratch buffer */
    k = srcBLen >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        x4 = (q15_t) * pIn2++;
        *pScr2++ = x4;
        x4 = (q15_t) * pIn2++;
        *pScr2++ = x4;
        x4 = (q15_t) * pIn2++;
        *pScr2++ = x4;
        x4 = (q15_t) * pIn2++;
        *pScr2++ = x4;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = srcBLen % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        x4 = (q15_t) * pIn2++;
        *pScr2++ = x4;

        /* Decrement the loop counter */
        k--;
    }

    /* Fill (srcBLen - 1u) zeros in scratch buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));

    /* Update temporary scratch pointer */
    pScr1 += (srcBLen - 1u);

    /* Copy (srcALen) samples in scratch buffer */
    k = srcALen >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        x4 = (q15_t) * pIn1++;
        *pScr1++ = x4;
        x4 = (q15_t) * pIn1++;
        *pScr1++ = x4;
        x4 = (q15_t) * pIn1++;
        *pScr1++ = x4;
        x4 = (q15_t) * pIn1++;
        *pScr1++ = x4;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = srcALen % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        x4 = (q15_t) * pIn1++;
        *pScr1++ = x4;

        /* Decrement the loop counter */
        k--;
    }

#ifndef UNALIGNED_SUPPORT_DISABLE

    /* Fill (srcBLen - 1u) zeros at end of scratch buffer */
    arm_fill_q15(0, pScr1, (srcBLen - 1u));

    /* Update pointer */
    pScr1 += (srcBLen - 1u);

#else

    /* Apply loop unrolling and do 4 Copies simultaneously. */
    k = (srcBLen - 1u) >> 2u;

    /* First part of the processing with loop unrolling copies 4 data points at a time.
     ** a second loop below copies for the remaining 1 to 3 samples. */
    while(k > 0u)
    {
        /* copy second buffer in reversal manner */
        *pScr1++ = 0;
        *pScr1++ = 0;
        *pScr1++ = 0;
        *pScr1++ = 0;

        /* Decrement the loop counter */
        k--;
    }

    /* If the count is not a multiple of 4, copy remaining samples here.
     ** No loop unrolling is used. */
    k = (srcBLen - 1u) % 0x4u;

    while(k > 0u)
    {
        /* copy second buffer in reversal manner for remaining samples */
        *pScr1++ = 0;

        /* Decrement the loop counter */
        k--;
    }

#endif	/*	#ifndef UNALIGNED_SUPPORT_DISABLE	*/

    /* Temporary pointer for second sequence */
    py = pScratch2;

    /* Initialization of pScr2 pointer */
    pScr2 = pScratch2;

    /* Actual correlation process starts here */
    blkCnt = (srcALen + srcBLen - 1u) >> 2;

    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr1 = pScratch1;

        /* Clear Accumlators */
        acc0 = 0;
        acc1 = 0;
        acc2 = 0;
        acc3 = 0;

        /* Read two samples from scratch1 buffer */
        x1 = *__SIMD32(pScr1)++;

        /* Read next two samples from scratch1 buffer */
        x2 = *__SIMD32(pScr1)++;

        tapCnt = (srcBLen) >> 2u;

        while(tapCnt > 0u)
        {

            /* Read four samples from smaller buffer */
            y1 = _SIMD32_OFFSET(pScr2);

            /* multiply and accumlate */
            acc0 = __SMLAD(x1, y1, acc0);
            acc2 = __SMLAD(x2, y1, acc2);

            /* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            /* multiply and accumlate */
            acc1 = __SMLADX(x3, y1, acc1);

            /* Read next two samples from scratch1 buffer */
            x1 = *__SIMD32(pScr1)++;

            /* pack input data */
#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x1, x2, 0);
#else
            x3 = __PKHBT(x2, x1, 0);
#endif

            acc3 = __SMLADX(x3, y1, acc3);

            /* Read four samples from smaller buffer */
            y1 = _SIMD32_OFFSET(pScr2 + 2u);

            acc0 = __SMLAD(x2, y1, acc0);

            acc2 = __SMLAD(x1, y1, acc2);

            acc1 = __SMLADX(x3, y1, acc1);

            x2 = *__SIMD32(pScr1)++;

#ifndef ARM_MATH_BIG_ENDIAN
            x3 = __PKHBT(x2, x1, 0);
#else
            x3 = __PKHBT(x1, x2, 0);
#endif

            acc3 = __SMLADX(x3, y1, acc3);

            pScr2 += 4u;


            /* Decrement the loop counter */
            tapCnt--;
        }



        /* Update scratch pointer for remaining samples of smaller length sequence */
        pScr1 -= 4u;


        /* apply same above for remaining samples of smaller length sequence */
        tapCnt = (srcBLen) & 3u;

        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr1++ * *pScr2);
            acc1 += (*pScr1++ * *pScr2);
            acc2 += (*pScr1++ * *pScr2);
            acc3 += (*pScr1++ * *pScr2++);

            pScr1 -= 3u;

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;

        /* Store the result in the accumulator in the destination buffer. */
        *pOut = (q7_t) (__SSAT(acc0 >> 7u, 8));
        pOut += inc;
        *pOut = (q7_t) (__SSAT(acc1 >> 7u, 8));
        pOut += inc;
        *pOut = (q7_t) (__SSAT(acc2 >> 7u, 8));
        pOut += inc;
        *pOut = (q7_t) (__SSAT(acc3 >> 7u, 8));
        pOut += inc;

        /* Initialization of inputB pointer */
        pScr2 = py;

        pScratch1 += 4u;

    }


    blkCnt = (srcALen + srcBLen - 1u) & 0x3;

    /* Calculate correlation for remaining samples of Bigger length sequence */
    while(blkCnt > 0)
    {
        /* Initialze temporary scratch pointer as scratch1 */
        pScr1 = pScratch1;

        /* Clear Accumlators */
        acc0 = 0;

        tapCnt = (srcBLen) >> 1u;

        while(tapCnt > 0u)
        {
            acc0 += (*pScr1++ * *pScr2++);
            acc0 += (*pScr1++ * *pScr2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        tapCnt = (srcBLen) & 1u;

        /* apply same above for remaining samples of smaller length sequence */
        while(tapCnt > 0u)
        {

            /* accumlate the results */
            acc0 += (*pScr1++ * *pScr2++);

            /* Decrement the loop counter */
            tapCnt--;
        }

        blkCnt--;

        /* Store the result in the accumulator in the destination buffer. */
        *pOut = (q7_t) (__SSAT(acc0 >> 7u, 8));

        pOut += inc;

        /* Initialization of inputB pointer */
        pScr2 = py;

        pScratch1 += 1u;

    }

}

/**
 * @} end of Corr group
 */
